Prediction of radial stresses due to prestressing in PSC shells

Large prestressed concrete (PSC) shells, such as silos, containment structures are prestressed along their principal curvatures. Prestressing cables are provided in the thickness of the shell either in one or two directions. The stresses normal to the middle surface are generally neglected in the design of such shell structures. However, the development of radial tensile stresses at the time of prestressing can lead to possible delamination failure, if these stresses are excessive. This paper presents simple procedures to estimate the radial stress distribution due to prestressing. Two methods are presented: 'equilibrium of slice' and 'modified Lame,' the latter being more rigorous and applicable to both singly and doubly curved shells. The solutions obtained are in conformity with the results of finite element analysis published earlier. Finally, an attempt is made to determine the local tensile stress distribution at the periphery of the prestressing duct hole, which also contributed to the problem of delamination. (C) 2003 Elsevier B.V. All rights reserved.